The call of Pope Innocent III, in 1211, stirred up anew the spirit of the Crusaders, but efforts were now directed, in the first place, against the Sultan in Egypt. Damietta, which lay on the Tanitic mouth of the Nile, where the Moslim had a fort, was the scene of many struggles. From January, 1218, to November, 1219, it was occupied by the Franks. In the meantime, the emperor Frederick invaded Palestine on his own account, and in 1229 secured a truce by which the Christian pilgrims were once more enabled to travel to Jerusalem. The advantages which he received were forfeited, however, owing to quarrels among the Christians themselves. The Sultan marched on Gaza in 1244, and attacked Jerusalem, which was finally lost to the Christians. It was in vain that the French king Louis IX, in 1249, occupied Damietta and pillaged Ostracine, which altogether disappeared. But Louis was taken prisoner and the restoration of Damietta was part of his ransom. Changes among the Moslim rulers hurried on events. The Mongols, pressing in from the East, overthrew the Caliph of Baghdad and destroyed the Syrian kingdom. A descendant of the true Prophet was established on the throne of Egypt as a nominal ruler, while the general, Bibars († 1277), with the title of Sultan, extended his authority over the greater part of Arabia and Syria. Bibars successfully led the campaign against the Crusaders. Antioch fell in 1268, Tripoli in 1289, Acre in 1291. By these losses the spirit of the Crusaders was broken. Of the bishops of Sinai during this period, little is known. In succession to Simeon (I or II), John III ruled from 1265 to 1290, and was followed by Arsinius, who was a book lover. Several books in Greek which are now in the convent library were written at his instigation, and one of them was owned by him.[260] The next bishop was Simeon (II or III), who ruled from 1306 to 1324, and was followed by Dorotheus (1324-1333), who secured a _firmân_ from the Sultan,[261] and a bull from Pope John XXII, who was at Avignon at the time. In this bull, dated 1328, the pope called upon Hugh, king of Cyprus, to respect the rights which former kings of Cyprus had granted to the monks of Sinai. He also recognised their right of burial in the church of St. Simeon at Famagusta in Cyprus, and granted one year’s indulgence to pilgrims who visited the shrine of St. Katherine in Mount Sinai.